Onsite or Offsite Welding Repair Work on Exotic Metals

Onsite or Offsite Welding Repair Work on Exotic Metals from VJIKKS ENGG POWER (M) SDN BHD

Keywords: Heat Exchangers, Titanium, Tantalum

 Welding work on Exotic metals like Titanium,Tantalum,Zirconium,Niobium etc.,
has to be done by the well trained personnel and by following strict procedures.

For example a few important points related to welding on an exotic metal Tantalum:
-Tantalum must be welded to itself and certain other metal by resistance welding and to itself by Inergas arc welding.
-Acetylene torch welding is destructive to the metal.
-Because its melting point is 2700deg F higher than that of SAE1020 steel and its resistivity is only two thirds that of SAE1020 steel, tantalum requires a higher power input to accomplish a sound weld.
-The weld duration should be kept as short as possible in the range of one and ten cycles ( 60cps) to prevent excessive external heating.
-Where possible, the work should be flooded with water for cooling and reduction of oxidation.
- RWMA Class 2 electrodes are recommended with internal water cooling.
-The electrode contours should be kept of constant area and contour to prevent lowering of current and pressure densities.
- A common mistake in welding tantalum is to apply too much elctrode force which causes so little interface resistance that no weld is made.
- Extreme care must be taken to cover with an inert gas all surfaces which are raised above 600deg F by the welding heat.
- Helium,argon or a mixture of the two gases creates an atmosphere which prevents embrittlement by absorption of oxygen,nitrogen or hydrogen into the heated metal.
- Extremely high ductility can be obtained in welding chamber which can be evacuated and purged with inert gas.
- Where the use of a welding chamber is not practical,the heated surfaces can be protected by proper gas backed fixturing.

Keywords: Exotic Metals, Heat Exchangers, Tantalum, Titanium, Zirconium,



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